1. Field of the Invention
The present invention relates to a heavy-duty shear which is adapted to be attached to a backhoe and, more particularly, the present invention relates to a metal cutting shear with inner plow bolt supports for indexable blade inserts.
2. Background Information
Heavy-duty metal cutting shears of the type that are mounted on backhoes and powered by hydraulic cylinders for efficiently handling scrap are well known in the art. Examples of these types of shears can be found in U.S. Pat. Nos. 4,403,431; 4,450,625; 4,519,135; 4,670,983; 4,686,767; 4,897,921; and 5,197,193. These heavy-duty shears are designed for efficient handling and shearing of scrap, generally metal scrap, into usable sizes. For example, in dismantling an industrial building, metal scraps in the form of pipes of various diameters and lengths, structural beams, such as I-beams, channels, angles and the like, and sheet metal and sheet metal plate must all be efficiently handled and severed by the metal cutting shears. The metal cutting shears are additionally utilized for reducing automobile and truck frames, railroad cars and the like.
These prior art metal cutting shears typically use replaceable blade inserts having at least one cutting edge thereon. When the cutting edge of the blades is worn, the blade inserts can be removed and sharpened or replaced. U.S. Pat. No. 4,897,921 discloses the use of reversible, indexable blade inserts wherein each blade insert has multiple cutting edges thereon which can be indexed to the appropriate operative position. U.S. Pat. No. 5,197,193 discloses similar reversible blade inserts having multiple cutting edges. Typically, the blade inserts of the prior art are held in position by one or more plow bolts extending therethrough into the anvil portion of the fixed or movable blade of the shear. The blade insert is provided with a recessed portion to receive the head of the plow bolt. This attaching arrangement provides some difficulties in reversible blade inserts which are flipped to provide new cutting edges such as in U.S. Pat. Nos. 4,897,921 and 5,197,193 discussed above. These deficiencies can be clarified by reviewing the typical prior art blade insert attachment illustrated in FIG. 1. The reversible, indexable blade insert 10 includes at least one central bore 12 extending therethrough with a pair of generally frustoconically-shaped recesses 14 and 15 at opposite ends of the central bore 12. Each recess 14 and 15 has a shape corresponding to a bolt head 16 of a plow bolt 18. The outwardly facing recess 15 is adapted to receive the bolt head 16 of the plow bolt 18 therein as shown in FIG. 1. The threaded end 19 of the plow bolt 18 opposite the bolt head 16 receives a nut 20 in an anvil recess 21 to secure the blade insert 10 within an insert seat 22 of an anvil 24 of the fixed or movable blade of the shear. The inwardly facing recess 14 butts up against the anvil 24 in the insert seat 22. The inwardly facing recess 14 and the outwardly facing recess 15 will be reversed when the blade insert 10 is flipped over. The anvil 24 includes a bolt-receiving bore 25 extending from the insert seat 22 to the anvil recess 21 and is aligned with the central bore 12 to receive the plow bolt 18 therethrough. A high-collar lock washer 26 is also conventionally provided in the anvil recess 21 around the plow bolt 18 between the nut 20 and the anvil 24. This prior art configuration results in a significant unsupported section 28 along the plow bolt 18 due to the inwardly facing recess 14 adjacent the anvil 24. The unsupported section 28 is undesirable in view of the high cutting forces exerted on the blade insert 10. Additionally, the unsupported section 28 increases the likelihood of mispositioning of the blade insert 10 within the seat 22 and increases the likelihood of the blade insert 10 pulling out from the seat 22.
It is an object of the present invention to overcome the aforementioned drawbacks of the prior art. It is a further object of the present invention to provide an attachment assembly for a reversible, indexable blade insert which includes substantially complete support along the length of the plow bolts. Another object of the present invention is to provide a blade insert attachment assembly which positively locates the blade insert in the anvil seat and effectively increases the blade insert to anvil surface area to help prevent blade insert pullout.